DESCRIPTION: Previous research has identified a complex pattern of sensory modulation by cortical pathways. An important area of modulation is the dorsal column nuclei. Neurons in the dorsal column nuclei may receive input from either glutamergic or aspartergic cortical synapses. This input may occur on either interneurons or relay neurons. One area of the proposed research is to determine at the EM level, using multiple label techniques, the neurochemicals contained in afferents to identified subpopulations of dorsal column nuclei neurons. This initial work will be followed by identification of amino acid receptors that are expressed by dorsal column nuclei neurons. Immunocytochemical localization will be used, as well as in situ hybridization using oligonucleotide probes. Postembedding immunogold techniques are hoped to be developed to localize receptors at the EM level. Lastly, the proposal plans to continue analysis of NO neurons and confirm that all are indeed interneurons rather than neurons with other target areas. Again, using double label methodology, colocalizaton of NO with glycine rather than GABA in dorsal column nuclei neurons will be explored.